This invention is directed to the field of intraluminal devices having coatings which provide radiopacity or wear resistance, and, in particular, to guidewires or stents having these features.
In a typical coronary procedure a guiding catheter having a preformed distal tip is percutaneously introduced into a patient""s peripheral artery, e.g. femoral or brachial artery, by means of a conventional Seldinger technique and advanced therein until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. There are two basic techniques for advancing a guidewire into the desired location within the patient""s coronary anatomy, the first is a preload technique which is used primarily for over-the-wire (OTW) devices and the bare wire technique which is used primarily for rail type systems. With the preload technique, a guidewire is positioned within an inner lumen of an OTW device such as a dilatation catheter or stent delivery catheter with the distal tip of the guidewire just proximal to the distal tip of the catheter and then both are advanced through the guiding catheter to the distal end thereof. The guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary vasculature until the distal end of the guidewire crosses the arterial location where the interventional procedure is to be performed, e.g. a lesion to be dilated or a dilated region where a stent is to be deployed. The catheter, which is slidably mounted onto the guidewire, is advanced out of the guiding catheter into the patient""s coronary anatomy over the previously introduced guidewire until the operative portion of the intravascular device, e.g. the balloon of a dilatation or a stent delivery catheter, is properly positioned across the arterial location. Once the catheter is in position with the operative means located within the desired arterial location, the interventional procedure is performed. The catheter can then be removed from the patient over the guidewire. Usually, the guidewire is left in place for a period of time after the procedure is completed to ensure reaccess to the arterial location if it is necessary. For example, in the event of arterial blockage due to dissected lining collapse, a rapid exchange type perfusion balloon catheter such as described and claimed in U.S. Pat. No. 5,516,336 (McInnes et al), can be advanced over the in-place guidewire so that the balloon can be inflated to open up the arterial passageway and allow blood to perfuse through the distal section of the catheter to a distal location until the dissection is reattached to the arterial wall by natural healing.
With the bare wire technique, the guidewire is first advanced by itself through the guiding catheter untirthe distal tip of the guidewire extends beyond the arterial location where the procedure is to be performed. Then a rail type catheter, such as described in U.S. Pat. No. 5,061,395 (Yock) and the previously discussed McInnes et al., is mounted onto the proximal portion of the guidewire which extends out of the proximal end of the guiding catheter which is outside of the patient. The catheter is advanced over the catheter, while the position of the guidewire is fixed, until the operative means on the rail type catheter is disposed within the arterial location where the procedure is to be performed. After the procedure the intravascular device may be withdrawn from the patient over the guidewire or the guidewire advanced further within the coronary anatomy for an additional procedure.
Conventional guidewires for angioplasty, stent delivery, atherectomy and other vascular procedures usually comprise an elongated core member with one or more tapered sections near the distal end thereof and a flexible body such as a helical coil or a tubular body of polymeric material disposed about the distal portion of the core member. A shapeable member, which may be the distal extremity of the core member or a separate shaping ribbon which is secured to the distal extremity of the core member extends through the flexible body and is secured to the distal end of the flexible body by soldering, brazing or welding which forms a rounded distal tip. Torquing means are provided on the proximal end of the core member to rotate, and thereby steer, the guidewire while it is being advanced through a patient""s vascular system.
An important attribute for guidewires is sufficient radiopacity to be visualized under a fluoroscope, allowing the surgeon to advance the guidewire to a desired location. Unfortunately, the most suitable materials for guidewires, such as stainless steel, exhibit relatively low radiopacity. Accordingly, various strategies have been employed to overcome this deficiency. Portions of the guidewire, usually the shapeable tip, may be made from or coated with relatively radiopaque metals such as platinum, iridium, gold or alloys thereof. For example, a 3 to 30 cm platinum coil tip is frequently soldered to the distal end of the guidewire. Other intraluminal devices such as stents may make use of radiopaque gold plating. An obvious drawback of these prior art methods is the high expense and scarcity of these radiopaque metals and the difficulty and expense of manufacturing products from these materials. The requirement of both radiopacity and high strength and flexibility is likewise an impediment.
Guidewires often are used to cross hardened plaques or total occlusions. The prior art has achieved wear resistant tips, but generally only at the expense of other desirable properties. As a result, an additional important feature of guidewires is a wear resistant tip that does not otherwise constrain guidewire design.
Accordingly, there remains a need for guidewires or stents having sufficient radiopacity to allow visualization under a fluoroscope without the use of expensive metals such as platinum. Additionally, there is a need for guidewires having wear resistant surfaces. This invention satisfies these and other needs.
This invention comprises an intraluminal device having a performance enhancing coating deposited using physical vapor deposition (PVD) or chemical vapor deposition (CVD).
One aspect of the invention is an intraluminal device having a radiopaque coating applied to at least a portion of the device. In a presently preferred embodiment, the intraluminal device is a stent or a guidewire, preferably formed of stainless steel, and the coating is applied to the distal tip of the guidewire. Preferably, the radiopaque coating may comprise platinum, tungsten, iridium, tantalum, or the like.
In another aspect of the invention, a wear resistant coating comprising carbides such as tungsten carbide, titanium carbide, or nitrides such as titanium nitride is applied to an intraluminal device such as a guidewire. The invention also comprises the methods of making such intraluminal devices.
A variety of conventional guidewire and stent designs may be used, as for example the guidewires and associated devices for various interventional procedures disclosed in U.S. Pat. No. 4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.): U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams et al.); and U.S. Pat. No. 5,345,945 (Hodgson, et al.), and stents and associated devices disclosed in U.S. Pat. No. 5,514,154 (Lau et al.); and U.S. Pat. No. 5,476,505 (Limon), which are hereby incorporated herein in their entirety by reference thereto.
The radiopaque or wear resistant coatings of the invention deposited onto an intraluminal device preferably have a very uniform and smooth surface. Moreover, the coating may be extremely thin for improved device performance. The hard and wear resistant coatings of the invention provide a variety of properties in addition to wear resistance, including radiopacity, bending stiffness, and solderability. These and other advantages of the invention will become more apparent from the following detailed description and accompanying exemplary drawings.